Tumor microenvironment and the role of mesenchymal stromal cells

Solid tumors are generally composed of two major components: heterogeneous malignant cells and non-malignant stromal part. The latter comprises several types of non-malignant cells of mesenchymal, endothelial and immune origin and together with the extracellular matrix significantly affects the biological properties of the tumor. This minireview is focused on recent advances in the understanding the role of tumor stromal component and its particular cell types in the tumor behavior. It summarizes the impact of mesenchymal stromal cells and the ways of their potential contribution to the tumor biology. As their role in the tumor development and the effects on the tumor cells remain controversial, we review the recent experimental evidence regarding the crucial molecular factors which determine their role in the tumors.